Process for high speed wet spinning of acrylonitrile fibers

ABSTRACT

A PROCESS FOR PORDUCING ACRYLIC SYNTHETIC FIBERS WHICH HAVE A UNIFORM CROSS-SECTIONAL SHAPE AND LUSTER AT A HIGH SPEED COMPRISING EXTRUDING A SPINNING SOLUTION PREPARED FROM ACYLONITRILE POLYMERS INTO AN INERT GAS MEDIUM, THEN LEADING THEM INTO AN AQUEOUS COAGULATING BATH TO FORM UNORIENTED GEL FIBERS, WASHING WITH WATER, STRETCHING AND DRYING OBTAINED FIBROUS MATERIALS AND THEN RE-STRETCHING SAID FIBROUS MATERIALS IN THE PRESENCE OF STEAM.

United States Patent PROCESS FOR HIGH SPEED WET SPINNING OF ACRYLONITRILE FIBERS Keijiro Kuratani and Keitaro Fukushima, Saidaiji, Japan, assignors to Japan Exlan Company 'Limited Filed July 22, 1969, Ser. No. 843,437 Claims priority, application Japan, July 22, 1968, 43/ 52,011 Int. Cl. D01f 7/02 US. Cl. 264-182 2 Claims ABSTRACT OF THE DISCLOSURE A process for producing acrylic synthetic fibers which have a uniform cross-sectional shape and luster at a high speed comprising extruding a spinning solution prepared from acrylonitrile polymers into an inert gas medium, then leading them into an aqueous coagulating bath to form unoriented gel fibers, washing with water, stretching and drying obtained fibrous materials and then re-stretching said fibrous materials in the presence of steam.

(1) FIELD OF THE INVENTION This invention relates to an improved process for producing acrylic synthetic fibers.

More particularly the present invention relates to a process for producing acrylic synthetic fibers at a high speed comprising extruding a spinning solution prepared by dissolving acrylonitrile polymers in an inorganic solvent into air or an inert gas which is noncoagulative with respect to said spinning solution. The extruded solution is then lead into an aqueous coagulating bath so as to be coagulated as unoriented gel fibers which are then washed with water. The fibers are then stretched and dried and then re-stretched in steam.

(2) DESCRIPTION OF THE PRIOR ART With respect to the prior art, in U.S. Pat. No. 3,088,793, there is disclosed a process for producing acrylic synthetic fibers. Since the spinning solution extruded out of a spinnerette is not immediately coagulated as in an ordinary wet-spinning process wherein a spinning solution is extruded directly into an aqueous coagulating solution, the obtained gel fibers will be highly extruded in air or the inert gas before they are dipped into the coagulating bath. Therefore, it is possible to set the degree of extrusion much higher than in the ordinary wet-spinning process. However, in said US. Pat. No. 3,088,793, since the thermal stretching following the extrusion step is carried out in a hot-water bath, the thermal stretching multiplication is diflicult due to such troubles as frequent filament breaks when the fibers are thermally stretched at such high speed as, for example, more than 300 meters/minute. There also has been considerable difficulty in the actual operation in increasing the running speed (which shall be called a spinning speed hereinafter) of the thermally stretched fibers.

In the high speed spinning of fibers of less than 1 denier, for example, if unoriented gel fibers were stretched directly at a high stretching multiplication, in addition to the ditficulty discussed above, the breaking phenomenon will occur in fibers of low tensile strength and small deniers to such an extent that it will be impossible to carry on the spinning.

(3) STATEMENT OF THE INVENTION The present inventors have discovered that, in the case of extending a spinning solution through spinning orifices directly into air or an inert gas and giving a stretching action to the obtained gel fibers, in order to prevent the 3,701,820 Patented Oct. 31, 1972 above mentioned troubles accompanying the high speed spinning, the above discussed difiiculties can be overcome by integrally combining a re-stretching step in a steaming heat medium, a drying step for adjusting the water content in the fibers to be in a required range prior to said re-stretching step and further a primary stretching step for imparting a required orientation to the gel fibers prior to the drying step so that the fibers to be dried in said drying step will not be made brittle.

A main object of the present invention is to provide a practical process for spinning, at a high speed, acrylic synthetic fibers which have excellent high uniformity of fineness, strength, elongation and cross-sectional shape as compared with a conventional wet-spinning process.

Another object of the present invention is to provide a process for producing acrylic synthetic fibers having an excellent brightness or luster.

A further object of the present invention is to provide a process for producing at a high speed, acrylic synthetic fibers small in denier and of excellent uniformity with respect to fineness, strength and elongation.

These objects of the present invention are attained by extending a spinning solution prepared by dissolving acrylonitrile polymers in an inorganic solvent into air or an inert gas which is a noncoagulative gas for the spinning solution, then leading it into an aqueous coagulating bath to form the fibers, washing the obtained fibers with water, stretching said fibers to be more than 1.4 times as long in a heating medium at a temperature of 20 to C. then drying them so that the water content in the fibers may be less than 15% and further re-stretching the fibers in a steam heat medium at a temperature of 100 to C. so that the total stretching may be 5 to 16 times the original length.

(4) BRIEF DESCRIPTION OF THE DRAWING FIG. 1 depicts a flowsheet of the process. FIG. 2 depicts a different mode of the present process.

(5) DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1, a spinning solution which is extruded out of a spinnerette 1 passing through an inert gas or air is coagulated a coagulating bath 2 provided in below the spinnerette 1. Thus the coagulated unoriented gel fibers 9 are drawn out from the coagulating bath 2 with a godet roller 3, are washed with Water, then are stretched in a thermal stretching bath 4, are dried on a drying roller 5, then are re-stretched in a stretching apparatus 6 into which steam has been introduced and further are treated to relax them by dry heat with a relaxing roller 7.

In working the process of the present invention, it is necessary that the distance between the bottom surface of the spinnerette and the liquid surface of the coagulating bath should be made more than 0.2 cm., since otherwise the slightest vibration of the spinnerette device will cause the spinnerette to be dipped into the coagulating bath and it will be difiicult to carry on the spinning.

The coagulating liquid to be used in the present invention requires a temperature less than 30 C. Water or an aqueous solution of an inorganic solvent having a concentration of less than 20% is used as the coagulant liquid. When the coagulating bath temperature is higher than the above mentioned temperature, the spun fibers will be devitrified, further will become brittle and will lose toughness and ductility.

It is recommended that the viscosity of the spinning solution to be applied to the process of the present invention be in a range of 2x10 to 1X 10' centipoises of more preferably 4x10 to 2 l0 centipoises at 30 C. When the spinning solution viscosity at 30 C. is lower than KEIJIRO KURATANl ET AL Oct. 31, 1972 3,701,820

PROCESS FOR HIGH SPEED WET SPINNING OF 7 ACRYLONITRILE FIBERS Filed July 22, 1969 0 n O 4 O 0 F|G.I

INVENIORS KEIJIRO KURATANI KEITARO FUKUSHIMA ATTORNEYS aqueous solution of a thiocyanate having a concentration of 47 to 65% by weight so as to be at a rate of 15 to 35 parts per 100 parts of the spinning solution. Further, as an inorganic solvent to be used in the present invention, there can be enumerated a concentrated aqueous solution of such thiocyanate as sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate or calcium thiocyanate, of a mixture of such thiocyanates, of such inorganic salt as zinc chloride or lithium chloride or of sulfuric acid or nitric acid. In this invention the total stretching multiplication is defined as the product of the primary stretching ratio and the restretching ratio.

Examples of the present invention are illustrated as follows. However, the subject matter of the present invention is not restricted by these examples, and in these examples, parts and percentages are shown all by weight.

In the present invention, by integrally combining in a series suchrespective processes as in the above, it is possible to continuously spin acrylic synthetic fibers having a collapsed fiber structure, uniform cross-sectional shape and remarkable luster at such high spinning speed of 1500 m./min., for example, as has never been obtained in any conventional wet-spinning process. Together with excellent spinnability of the fibers which have finer deniers thereby, the advantages brought to the industry by the present invention are very valuable.

Example 1 A copolymer (where [1 ]=1.4 in dimethylforamide at 30 C.) consisting of 91.4 parts of acrylonitrile, 8.6 parts of methyl acrylate and 0.4 part of sodium arylsulfonate was dissolved in an aqueous solution of 50% sodium thiocyanate to prepare a spinning solution having a concentration of 17% of the copolymer. The viscosity of the spinning solution at 30 C. in this case was 523x centipoises. Said spinning solution was warmed to 65 C., was extruded into air at the rate of 118 g./min. with a clearance of 1.0 cm. between the bottom surface of the spinnerette and the liquid surface of the coagulating bath by using a spinnerette having 50 spinning orifices of a diameter of 0.12 mm. and orifice distance of 3.77 mm. The extruded material then was dipped into an aqueous solution of 12% sodium thiocyanate kept at 3 C. to form the fibrous materials. Said fibers were drawn at a peripheral speed of 150 m./min. on a godet roller, were washed with water, then were stretched to be 4 times as long, then were dried for 45 seconds in contact with the peripheral surface of a roller heated to 120 C. and further were re-stretched to be 2.5 times as long in steam at 143 C. The spinning speed in this case was 1500 m./min. Then, in steam at 120 C., the obtained fibers were relaxed for minutes to obtain acrylic synthetic fibers of a monofilament fineness of 3 deniers. This fiber is hereinafter called fiber A.

On the other hand, the fibers were spun under the same spinning conditions as were mentioned above by using the same spinning solution and spinnerette as were used in producing the above mentioned fiber A, were coagulated, were drawn at a peripheral speed of 150 m./ min. of a godet roller, then were washed with water and were stretched to be 10 times as long in steam at 127 C. The spinning speed in this case was 1500 m./min. They were then dried for 1 minute in contact with the peripheral surface of a roller which was heated to 115 C. and further were treated to relax for 15 minutes in steam at 120 C. to obtain acrylic synthetic fibers which had monofilament fineness of 3 deniers. This fiber is hereinafter called fiber B.

Then the same polymer as was used in producing the fiber A was dissolved in an aqueous solution of 44% sodium thiocyanate to prepare a spinning solution having a concentration of 11.3% of the copolymer. The viscosity of this spinning solution at 30 C. was 45 x10 centipoises. Said spinning solution was warmed to 70 C. and was extruded directly into an aqueous solution of 12% sodium thiocyanate at a temperature of -3 C. while maintaining an amount of delivery of 15.9 g./min. by using a spinnerette having 50 spinning orifices of a diameter of 0.09 mm. and coagulated to form the fibers. The fibers were drawn at a peripheral speed of 13.5 m./ min. of a godet roller, were then washed with water and were stretched to be 10 times as long in hot water at 98 C. The spinning speed in said stretching was 135 m./min. The fibers then were dried for 1 minute in contact with the peripheral surface of a roller heated .to C. and further were treated to relax for 15 minutes in steam at C. to obtain acrylic synthetic fibers of a monofilament fineness of 3 deniers. This fiber is hereinafter called fiber C.

Further, the fibers were spun under the same spinning conditions as in spinning the fiber C by using the same spinning solution and spinnerette as were used in producing the fiber C, were coagulated, were washed with water, were stretched to be 4 times as long in boiling water, then were dried for 45 seconds in contact with the peripheral surface of a roller heated to 115 C. and were re-stretched to be 2.5 times as long in steam at 143 C. The spinning speed in this case was m./min. Then they were heatrelaxed in the same conditions as in producing the fiber A to obtain acrylic synthetic fibers of a monofilament fineness of 3 deniers. This fiber is called as fiber D.

The luster, cross-sectional shaped and physical proper: ties of each of the fibers A, B, C, and D obtained by the above mentioned respective examples were shown in Table 1.

2 Nonuniform e.g. guitarshaped.

Cross-sectional shape 1 All circular.

In this example, the luster was measured by the following method:

(1) 1 g. of fibers cut to be 4 to 5 cm. long were arranged and were ironed.

(2) The above arranged fibers were pasted at both ends to a cardboard with a binder.

(3) The luster of the fibers pasted to the above mentioned cardboard was measured with a Murakami MG5 luster meter (made by Murakami Coloring Technical Laboratory) As evident from the description in Table 1, the fibers A and B obtained by the spinning process wherein a spinning solution having as a main component an acrylonitrile polymer dissolved in an aqueous solution of an inorganic salt is once extruded into air or an inert gas which is a noncoagulative gas for said spinning solution and is then coagulated in an aqueous coagulating bath have the same filament properties as of the fibers C and D produced by a wet-spinning process wherein a spinning solution of an acrylonitrile polymer is extruded directly into an aqueous coagulating liquid and have a luster far superior to that of the above mentioned fibers C and D obtained by the ordinary wet-spinning process. Further, in comparing fiber B in which the stretching is carried out directly in steam with fiber A in which the fibers first are stretched in hot water or in the presence of a dry heat medium, are dried and then are re-stretched with steam as in fiber A, it will be clear that the luster of the fibers in the latter case are remarkably improved.

Example 2 v The same spinning solution as was used in the production of the fiber A in Example 1 was used. Said spinning solution was warmed to 70 C., was extruded into air while maintaining the rate of 17-6 g./min. A clearance of 0.8 cm. was maintained between the bottom surface of the spinneretteand the liquid surface of the coagulating bath. A spinnerette having 80 spinning orifices of a diameter of 0.1 mm. and orifice distance 2.6 mm. yielded as long in steam at 143 C. The spinning speed in the re-stretching was 500 m./min. The thus obtained fibers were preheated for 1 second in contact with the peripheral surface of a heated roller and then were treated to relax for 2 seconds in contact with a relaxing roll heated to fibrous material which was then dipped into an aqueous 5 250 C. so as to shrink by to obtain acrylic synsolution of 12% sodium thiocyanate at 5 C. to form thetic fibers of a monofilament fineness of 3 deniers. fibers. Said fibers then were drawn in the condition of The obtained fiber was of a luster of 71, knot strength peripheral speed of 150 m./min. of a godet roller, and of 1.7 g./d. and Youngs modulus of 1.60 g./d. in hot were washed with water and further were stretched to be 10 water and the cross-sections of the respective fibers were 4 times their length in boiling water. Then said fibers all circular and showed a remarkable uniformity.

were primarily dried for 30 seconds in contact with the Example 4 peripheral surface of a roller heated to 115 C. and

were re-stretched to be 2.5 times as long in a steam The Same SPlmhhg sohltloh as Was used 111 Example atmosphere at 35 c The Spinning speed in Said 15 1-A was warmed to 70 C. and was extruded into air with stretching 500 Then said fib were a clearance of 1.0 cm. between the bottom surface of the oridarilydried for 1 second in contact with the peripheral spinnerette and the liquid Shffaee 0f the coagulating bath surface of a drying roller heated to 170 C. and were y e SPihefette having 50 Pi1111i11g orifices 0t 3 shrunk by 10% with. a relaxing roller. heated to 260 0. (hamster of and Orifice defiance of 4 The to obtain acrylic synthetic fibers of a monofilament fineextruded fibers were then PP Into an aqueous Solu' ness f deniem This fib is called as fib E. tion of 12% sodium thiocyanate at a temperature of 5 C.

In the process of producing fiber F all conditions were so as to be eoegulated, were drawn with a godet roller, exactly the same as in the process of spinning the fiber and were washed with water and further Primarily were E except that the primary drying temperature was 85 C, stretched to be 4 times as long in boiling water. Then The luster, cross-sectional shape and physical properties the fibers were drled for 45 Seconds in contact with a of each obtained acrylic synthetic filament are shown in roller heated to and were l'e'stretched and Table ther were treated to relax for 15 minutes in a steaming heat atmosphere at 120 C. to obtain acrylic synthetic TABLE 2 fibers of a monofilament fineness of 3 deniers. The possi- F E bility of the continuous spinning was investigated by vary- Primary drying temperature Q) 85 n5 mg as 1n the following table the amount of delivery, the Water content after primary drying (percent) 20.3 5.1 peripheral'speed of the godet roller, the stretching condifigig g -m -ag ggg g zga ags: z tiOI IS in the re-stretching step and the stretching multipli- Monofilament deniers .45 2. 53 cation in the process of producing these fibers. gggggfiitff :1: -6; From these experiments, it is proved that, in case boilx An 6 U1 ing water is used as a heating medium in the re-stretching step, at a spinning speed of 752 m./min., the filament TABLE 3 Total Peripheral stretching speed of multipli- Amount of the godet cation Spinning Stretching multiplication Stretching multiplication delivery roller rate speed and possibility of stretching and possibility of stretching (g./m.1n.) (m./mm.) (tunes) (m./rmn.) in steam at 140 C. in a boiling water medium 94 4 376 1 time possible 1 time possible. 94 6 564 1.5 times possible 1.5 times possible. 94 8 752 2 times possible 2 times impossible. 94 12 1, 128 3 times possible- 3 times impossible. 94 16 1,504 4 times possible 4 times impossible.

It is clear from the description in this example that, breaks so often that the stretching is impossible, whereas, in case the primary drying temperature is low and the in a steaming heat medium, even if the re-stretching speed water content in the fiber immediately after the primary were further elevated, the stretching is satisfactory. drying step is shown to be more than 15%, the obtained fiber has many voids and is inferior in the luster. Example 5 The same spinning solution as in Example l-A was Example 3 warmed to 70 C. and was extruded so as to be coagulated as fibers into an aqueous solution of 12% sodium The same spinning solution as was used in Example thiocyanate at a temperature of 5 C. while maintaining 1-A was warmed to 6 5 C. and was extruded into air at an amount of delivery of 3.9 g./min. with a distance of the rate of 39 g./min. with a clearance of 1.0 cm. be- 1.0 cm. between the bottom surface of the spinnerette tween the bottom surface of a spinnerette having 50 and the liquid surface of the coagulating bath by using spinning orifices of a diameter of 0.15 mm. orifice disa spinnerette having 8 spinning orifices of an orifice tance of 3.77 mm. and the liquid surface of the coagulatdiameter of 0.1 mm. and orifice distance of 4 mm. In said ing bath. The obtained fibrous materials then were dipped coagulating bath step, in order to make the direction of into an aqueous solution of 12% sodium thiocyanate at the fiow of the coagulating liquid coincide normally with 5 C. to form fibers. Said fibers were drawn at a periphthe direction of the advance of the filamentary materials, eral speed of 50 m./min. of a godet roller, Were washed such flowing bath type spinning apparatus as is exempliwith water and then were stretched to be 1.2 or 2.0 times fied in FIG. 2 was also used. The depth of the coagulatas long in boiling water. Then said fibers were heated ing bath fiow in the funnel body was 14 cm., the inside and dried for 30 seconds on a roller heated to C. diameter of the narrowest part of the tube part was 0.6 The fibers which were stretched to be 1.2 times as long cm. and its length was 30 cm. Where the coagulating in said stretching step became so brittle and its monoliquid was made to flow down by such flowing bath type filaments broke so often that it was very difficult to treat spinning apparatus, the average flowing speed of the the fibers in the subsequent steps. 0n the other hand, the coagulating liquid being 102 m./min. Then the coagufibers which were stretched to be 2.0 times as long did 75 lated fibers were drawn at a peripheral speed of m./

not become brittle and could be re-stretched to be 5 times min. of a godet roller, were washed with water, then were stretched to be 3.2 times as long in boiling water. The thus obtained fibers were dried for 30 seconds in contact with the peripheral surface of a roller heated to 110 C. and then were re-stretched to be 2.5 times as long in steam at 137 C. After the said re-stretching step, the spinning speed was 1090 m./min. Then said fibers were treated to relax for 1 second on a relaxing roller heated to 260 C. so as to shrink by 15%, thus an acrylic synthetic fiber of a monofilament fineness of 0.8 denier is obtained.

The values of the characteristics including the luster of the obtained fiber were as in the following Table 4.

TABLE 4 Deniers Dry elongation (percent Knot strength (percent).

Example 6 The same spinning solution as in Example l-A was extruded into air by varying the amount of delivery as hown in Table with a clearance of 1.0 cm. between the bottom surface of the spinnerette and the liquid surface of the coagulating bath by using a spinnerette having 8 spinning orifices of a diameter of 0.1 mm. and dipped into an aqueous solution of 12% sodium thiocyanate at a temperature of 3 C. In this case, such flowing bath type spinning apparatus as is shown in FIG. 2 was used so that the direction of the flow of the coagulating liquid might be normally the same as the direction of the advance of the filamentary materials. The depth of the coagulating bath in the funnel body was 14 cm., the diameter of the narrowest part of the tube part 13 was 0.6 cm. and its length was made 30 cm. The coagulating liquid was fed through the coagulating liquid feeding pipe 14 while always keeping the constant liquid height. The average flowing speed of the coagulating liquid was 102 cm./min. The peripheral speeds of the godet roller corresponding to the respective amounts of delivery and the optimum peripheral speeds of the godet roller at which the continuous spinning is possible are shown in Table 5.

Further, the maximum peripheral speeds of the godet roller corresponding to the amount of delivery of the spinning solution and the maximum pheripheral speeds of the godet roller at which the continuous spinning is possible if the flowing bath type spinning apparatus shown in the Example 5 is not used are also mentioned in Table 5.

TABLE 5 Peripheral speed of the godet roller at which the continuous spinning can be made stable Where the flowing bath type spinning apparatus is not used (m./min.)

Maximum peripheral speed of the godet roller Where the flowing bath type spinning apparatus is used (m./min.)'

Amount of delivery (cc/min.)

From this experiment, it will be clear that, when making the coagulating liquid flow in the same direction as the direction of the advance of the fiber filaments, the peripheral speed of the godet roller, that is, the draw ing speed can be greatly elevated to be higher than when using no flowing bath type spinning apparatus. The results of this experiment show that the simultaneous use of a flow bath type spinning step in Working the process of the invention of the present application greatly increases the spinning speed and at the same time makes it possible to produce fibers which have low deniers.

What is claimed is:

1. A high speed process for producing acrylic fibers wherein the acrylic polymer used is polyacrylonitrile or a copolymer containing at least by weight of acrylonitrile the remainder being other unsaturated vinyl monomers copolymerizable with acrylonitrile, said polymer having a molecular weight corresponding to an intrinsic viscosity [1 of 0.4 to 4.0 in dimethyl formamide at a temperature of 30 0., characterized by the following steps performed in continuous sequence:

(a) extruding a spinning solution through spinning orifices which is prepared by dissolving said polyacrylonitrile or copolymer in an aqueous solution of sodium thiocyanate capable of dissolving the same, said polymer solution having a viscosity of 2 x 10 to 1x10" centipoises, into air and in the form of continuous fibers;

(b) introducing said fibers into an aqueous solution of sodium thiocyanate having a temperature less than 30 C. to coagulate same;

'(c) withdrawing said coagulated fibers with a godet roller having a peripheral speed of at least 50m./ min.;

(d) washing said fibers with-water;

(e) stretching said fibers from 1.4 to 4.0 times their original length at a temperature of 20 to C.;

(f) drying said fibers to a water content of less than (g) and further restretching said fibers in the presence of 100 to C. steam so that the total stretching multiplication is 5 to 16 times.

2. The process of claim 1 wherein the first stretching step (e) is performed in steam or hot water or a dry atmosphere.

References Cited UNITED STATES PATENTS 3,037,240 6/1962 Stoy 264342 RE UX 3,558,761 1/1971 Tabara et a1.v 264-342 R-E X 3,104,938 9/ 1963 Kocay et a1. 264182 3,414,645 12/1968 Morgan 264-210 F 3,447,998 6/ 1969 Fitzgerald et a1. 264-182 X 3,516,903 6/1970 Jones et a1. 264-l82 X 3,523,150 8/1970 Vigneault 264210 F 3,080,210 5/1963 Ucci 264-203 3,088,793 5/1963 Knudsen et al. 264-182 3,111,366 11/1963 Fujita et a1. 264-182 PHILIP E. ANDERSON, Primary Examiner U.S. Cl. X.R.

260-308 R, 32.4; 264-210 F, 342 RE 

